1999 Final Exam Key

1999 Final Exam Key -...

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Unformatted text preview: Name_________________KEY___________________ ID # ____________________________________ Organic Chemistry 3301 Spring 1998 Final EXAM 350 Points 13 Pages plus Table 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 20 points 30 points 30 points 30 points 30 points 30 points 30 points 45 points 45 points 30 points 30 points __________________ __________________ __________________ __________________ __________________ __________________ __________________ __________________ __________________ __________________ __________________ Total 350 points __________________ Chem 3301, Spring 1998, Final Exam, Page 1 Name_________________KEY___________________ 1) (20 points) Draw a Lewis dot structure for each of the following molecules; show all lone pairs. Indicate the hybridization at all atoms except hydrogen, chlorine, and fluorine. (a) CH3OH sp 3 s p3 H HCOH H (b) CH3CCCH2COCH3 s p3 s p3 s p2 s p3 H HOH HCCCCCCH H H H sp s p2 2) (30 points) Give resonance structures (no dipolar forms) for the following compounds. (a) H3C C C N H H3C C C N H O (b) H H O H H H O (c) Chem 3301, Spring 1998, Final Exam, Page 2 Name_________________KEY___________________ 3) (30 points) The structure of Methoprene and an isomer of this compound are shown below. Methoprene is used to kill mosquitos in marshy areas. Recently, it has been proposed that some degradation products of Methoprene are responsible for causing the deformities in frogs that are being observed in lakes in Minnesota. O O Methoprene O O Degradation product of Methoprene O O (a) What is the molecular formula of Methoprene? C19H34O3 (b) Identify the functional groups indicated by the arrows. Ether Alkene O Ester O O (c) Should the double bond in Methoprene indicated by the arrow be designated E or Z? E Alkene O O O (d) Which of the following terms best describes the relationship between Methoprene and its degradation product: structural isomers, enantiomers, geometric isomers, or conformers. Write your answer below. Geometric isomer Chem 3301, Spring 1998, Final Exam, Page 3 Name_________________KEY___________________ 4) (30 points) The structure of Chloramphenicol, an antibiotic that interferes with ribosomal function, is shown below. OH OH Cl O 2N H N O Cl Chloramphenicol (a) Identify the functional groups indicated by the arrows. OH OH Cl O 2N H N O Amide Cl Alcohol (b) Circle the chiral center(s) in chloramphenicol. For each center, indicate whether the configuration is R or S. R OH OH Cl O 2N H N O Cl R (c) Draw the enantiomer of chloramphenicol OH OH Cl O 2N H N O Cl (d) Draw one diastereomer of chloramphenicol. OH OH Cl O 2N H N O Cl or O 2N H OH OH Cl N O Cl Chem 3301, Spring 1998, Final Exam, Page 4 Name_________________KEY___________________ 5. (30 points) Indicate the reagent(s) you would use to accomplish the following conversions. Give your answers in the boxes supplied. 1) BH3-THF 2) NaOH, H2O 2 OH OsO4, H2O 2 or KMnO4, cold/dilute OH OH H 1) Hg(OAc)2, CH3OH 2) NaBH4 OCH3 HBr, ROOR Br C H3C O3H, H2O HO OH H KMnO4, warm/conc. HO O + O Chem 3301, Spring 1998, Final Exam, Page 5 Name_________________KEY___________________ 6. (30 points) Draw the major product for each reaction between the compound shown below and the reagents indicated. Indicate stereochemistry where appropriate. Draw only one enantiomer when both are formed. H2 / Pt MCPBA O C H3 Br2, H2O H OH Br H 1) BH3-THF 2) NaOH, H2O 2 H C H3 OH 1) O3 2) (CH3)2S H O O HCl Cl Chem 3301, Spring 1998, Final Exam, Page 6 Name_________________KEY___________________ 7. (30 points) Indicate the major product or reagents necessary for each reaction given below. OH O O O 1) NaBH4 2) H3O + O O Product O H 1) CH3C H2MgBr 2) H3O + OH Reagents SOCl2 OH Reagents Cl 1) Na 2) CH3C H2C H2Br OH Reagents (2 steps) O 1) LiAlH4 2) H3O + O O OH Reagents (2 steps) OH 1) TsCl, pyridine 2) NaOH Product Chem 3301, Spring 1998, Final Exam, Page 7 Name_________________KEY___________________ 8. (45 points) Propose a mechanism for the following reactions. Show all steps including proton transfer steps. Show all lone pairs and indicate the formal charges on all intermediates. OH H2S O4 O (a) O O H OH O O HOSOH O HgOAc OH Hg(OAc)2 Step 1 O NaBH4 Step 2 O OH2 O O C H2 O H H O HOSO O HgOAc (b) Provide mechanisim for step 1 only OH Hg OAc OH Hg OAc OH AcO Hg OAc HgOAc O O HgOAc H AcO Chem 3301, Spring 1998, Final Exam, Page 8 Name_________________KEY___________________ OH H3O + (c) O HO O H H H O H O HO OH HO HO HO H O H H HO HO H 9. (45 points) Show how you would synthesize the following products from the starting materials given and any additional compound 4 carbons or less. This means you must indicate the reagents needed. You may wish to show the intermediates in your synthesis but do not show any mechanisms. OH (a) O OH PCC H 1) CH3C H2MgBr 2) H3O + OH LiAlH4, TiCl4 or 1) TsCl, pyridine 2) LiAlH4 Chem 3301, Spring 1998, Final Exam, Page 9 Name_________________KEY___________________ OH (b) Br OH H2S O4 MCPBA O 1) CH3C H2MgBr 2) H3O + PBr3 Br OH HO OH Starting Material Final Product (c) O OH PCC H 1) Hint: The above compound is an intermediate in the synthesis of the final product OH MgBr H2S O4 2) H3O + O MCPBA 1) CH3C H2MgBr 2) H3O + HO Chem 3301, Spring 1998, Final Exam, Page 10 Name_________________KEY___________________ 10. (30 points) Consider the compounds shown below: Hb O O Compound 1 Hb Hc Ha Hc O Hd Ha Compound 2 (a) For compound 1, indicate which type of proton (Ha, Hb or Hc) would give the most downfield signal. Hb (b) For compound 1, indicate the multiplicity (singlet, doublet etc) for each type of proton. Ha: Hb: H c: doublet septet singlet (c) For compound 2, indicate the multiplicity for each type of proton. Assume that the coupling constant Jab is equal to the coupling constant Jbc. Ha: Hb: H c: H d: triplet sextet triplet singlet (d) For compound 2, indicate the multiplicity for the Hb protons. However, in this case assume that the coupling constant Jab is much greater (more than two times) than the coupling constant Jbc. Give your answer as a number, not a word. 12 Chem 3301, Spring 1998, Final Exam, Page 11 Name_________________KEY___________________ 11. (30 points) Consider the compounds shown below: Compound 2 + Compound 3 Both have molecular formula C8H15Br HBr Compound 1 (a) Treatment of compound 1 with HBr produces two products, compound 2 and compound 3, with the molecular formula C8H15Br. Draw the structures of both of these products. Indicate stereochemistry in your answer. Do not label your products compound 2 or compound 3. Br Br (b) As shown below, treatment of compound 2 with NaOH gives a new product, compound 4. Treatment of compound 3 with NaOH gives a different product, compound 5. Draw the structures of both of these new products. Do not label your products compound 4 or compound 5. Compound 2 NaOH Compound 3 NaOH Compound 4 C 8H14 Compound 5 C 8H14 (c) Compound 5 is more stable than compound 4. With this information, you should be able to deduce the identity of compounds 2, 3, 4 and 5. Draw these compounds in the boxes. Br Br Compound 2 Compound 3 Compound 4 Compound 5 Chem 3301, Spring 1998, Final Exam, Page 12 Name_________________KEY___________________ (d) Use Newman projections to explain why compound 2 gives rise to compound 4 and why compound 3 gives rise to compound 5. Use the templates provided and provide a brief explanation. Compound 2 cannot have both Br and H in axial position for E2 reaction so elimination occurs by proton abstraction at C6 to give a trisubstituted alkene. Compound 3 can adopt a conformation that places Br and H in axial positions and leads to elimination between C1 and C2 to give the tetrasubstituted alkene. H H H H H Compound 3 H H H H Br Compound 2 C H3 C H3 H Br C H3 C H3 Chem 3301, Spring 1998, Final Exam, Page 13 ...
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This note was uploaded on 11/30/2010 for the course CHEM 2301 taught by Professor Gao during the Spring '07 term at Minnesota.

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